ESR1 and neoplasm: Accordingly, reduced BRCA1 expression or mutation has been frequently reported in sporadic breast cancer.1, 2 BRCA1 silencing or mutation is also associated with basal-type breast cancer phenotype in which the tumour cells express no estrogen receptor (ER), progesterone receptor (PR) nor human epidermal growth factor receptor 2 (HER2) receptor, high p53 mutation and poor prognosis.3 The mechanisms linking BRCA1 loss/mutation to tumorigenesis are not clearly understood.